Method and apparatus for making finned tubing



June 1, 1948. R. M. WALLACE METHOD AND APPARATUS FOR MAKING FINNED TUBING Filed lay so. 1944 2 Sheets-Sheet 1 INVENTOR ROBERT M. WALLA CE Mia aka AfToRNEYs .l I .I II II W 2 Sheets-Sheet 2 R. M. WALLACE June I, 1948.

amnion AND APPARATUS FOR MAKING FINNBD 'rusme Filed lay 30, 1944 U ;NVENTOR ROBERT M. WALLACE I BY s ame, 2611; WW 4 @1004 ATTORNEYS Patented June 1,1948

METHOD arm mama FINNED TUS FOR MAKING TUBING Robert M. Wallace, Massillon, Ohio, in... to

The Griscom-Russell O N. Y., a corporation of Delaware ompany, New York,

Application May 30, 1944, Serial No. 538,053

This invention relatesto method and alibiratus for making finned tubing and has for its object to provide a method and apparatus for expeditiously and cheaply manufacturing finned tubing for heat exchangers and other purposes wherein the fin consists of a continuous spiral rib with the plane of the rib that is, the plane in which the radial elements of the rib lie, at an angle to the axis of the tubing instead of being perpendicular thereto as is customary.

In the preferred embodiment of my invention the spirally wound fin is continuously welded at its base to the wall of the tubing, and one of the important features of my invention is the novel method and apparatus for rapidly and effectively welding the edge of the fin to the wall of the tubing. This portion of my invention may be readily employed in the manufacture of the ordinary heat exchanger tubing with the plane of the fins normal to the axis of the tubing.

Another important feature of -my invention is the method and apparatus for winding and spacing of the fin on the tubing with the plane of the fin at an angle to the axis of the tubing. This feature may be employed without the welding step or in conjunction with other means of join-v ing the fin to the tubing.

In the accompanying drawings I have illustrated the successive steps carried out in the practice of my improved method for the manufacture of the tubing of the type specified and have also illustrated certain novel features of the apparatus employed in carrying out such steps.

Referring to the drawings;

Fig. 1 shows the flat coiled fin ready for application to the tube;

Fig. 2 illustrates the procedure followed in spacing the fin along the wall of the tube;

F18. 3 illustrates the method of welding the fin to the tube;

Fig. 4 is a perspective view of a short length of the finished tube;

Fig. 5 is a perspective viewof the welding apparatu preferably employed for carrying out the step of Fig. 3;

Fig. 6 is .a plan view of the fin winding apparatus; and v Fig. 7 is a vertical sectional view on line 1-1 of Fig. 6.

In carrying out my preferred method I precoil a strip of metal of the desired width and thickness in the form of a continuous fiat helix, as illustrated in Fig. 1, for which purpose I may advantageously employ the coiling machine method disclosed in U. 8. Patent No. 1,878,233

3 Claims. (01. 29-1573) granted September 20, 1932 to Edward a De- Wald. For forming finned heat exchanger tubes wherein the plane of the fin is normal to the axis of the tube, the inner diameter of the fin helix will be substantially the same as or but slightly greater than the outer diameter of the tubing so that the pre-coiled ribbon may be easily slipped over the tube. During the application of the fin to the tube to form finned tubing of this type, additional work is performed on the fin itself involving pulling it down to tightly grip the periphery of the tubing. The outer portion of the width of the'fin is stretched b suitable guide rolls and knurling rolls of the fin winding head. When, however, the plane of the fin is to be inclined to the axis of the tubing, the inside diameter I of the flat helix is somewhat greater than the outer diameter of the tube so that when the fin helix is stretched along the tube to give the desired pitch tothe fin, as indicated in Fig. 2, the inner edge of the coiled ribbon will contact the surface of the tube and the plane of the fin will be deflected from the normal to whatever extent is desired, In this specification and the appended claims, the plane of'the fin or strip is employed to denote a plane extending transverse- 1y of the tube and tangent to the fin strip along a radial element thereof. The relation between the inside diameter of the fin helix and the outside diameter of the tube has a direct relationship to the pitch of the fin and the angle of defiection thereof. No additional work is performed on the fin proper while it is spaced along the tube to form an inclined plane fin structure.

After the hat coiled helix is slipped over the t the e d of the fin at the left as shown in Fig. 6 is pulled out along the wall of the tubing, forming a space between the first turn of the helix and the next adjacent turn of a width to give the desired pitch to the fin. As the fin is so pulled out the plane of the fin will be inclined to the perpendicular to an extent depending upon the internal diameter of the helix and external diameter of the tube.

The leading end of the fin is spot-welded to the tube as indicated at 2 and the adJacent end of the tube is clamped in the chuck 3 on the end of a rotating shaft 4. The other end of the tube is supported for rotation on a bearing 5 mounted at the opposite end of the machine frame. The machine is also provided with a traveling bed 6 underlying the tube and on which is supported a spacer guide roller 1 whose working or finengaging face or part 8 includes a straight element extending radially of the tube and inclined to its axis of rotation of the extent to which the plane of the fin is to be inclined to the axis of the tube. The small end of the face 8 of the roller 1 is provided with an annular shoulder 9 disposed at an angle to said face which engages the outer edge of the fin and so forces the fin to the desired angular position in contact with the inclined face 8. The machine bed also carries a block 9' carrying a tube supporting arm 9" engaging the tube surface opposite the guide roller 1 to hold the tube against lateral displacement from the pressure exerted by the guide roller against the fin.

The movement of the machine bed is correlated with the rotation of the shaft 4 to give the desired pitch to the spiral fin and as the opera- 1 tion proceeds, the spacer guide'roller l stretches the coils of the fin lengthwise of the tube to the desired pitch and wraps the fin tightly around the tube. At intervals as the winding proceeds, a spot weld, as indicated at I0, is made to hold the fin against displacement on the tube until the final welding is accomplished.

After the fin has been wound and spot welded I to the tube as indicated, it is permanently attached to the tube by a continuous weld at the junction between the base of the fin and the contiguOuS tube surface, as indicated at H in Fig. 3. To accomplish this welding operation expeditiously and accurately, I preferably employ a machine of the design illustrated in Fig. 5. This machine consists of a frame l5 having a power-driven spindle l6 at one end and an aligned rotary bearing ll at the other end for supporting and rotating the tube. The tube is connected to the shaft i6 by a chuck l8 whereby the tube with the fin spot welded to it at intervals may be continuously rotated. The supporting carriage l5 has rails is at each side which are parallel to the tube supporting shafts l6 and i1, and mounted for travel on the rails I9 is a carriage 20 which carries the welding mechanism.

=The fioor 2| of the carriage 20 overlies the tube and its attached fin and carries a welding control box conventionally indicated at 22. Se-

' cured to the floor 2| through a hinged plate 2! and a bracket 23' is a support 23 for the welding electrode 24 which is carried by a contactor nozzle 24' so secured to the support 23 that the electrode projects downwardly at an angle of approximately 90% to. the inclined fin on the tube beneath it. 1

An arm 30 is fixed at one-end to a plate 2| hingedly secured to the carriage'Zfl and the arm extends transversely of the carriage floor 2| and is removably held down in contact with the floor 'by a spring 3| connected between the arm 30 and a. bracket 32. A roller33 is rotatably supported to depend from the under surface of the arm 30 in line with the tube, and is so disposed as to bear along the outer edge of the fin on the tube. As the tube is rotated, the fin acts as a screw to propel the carriage 2| along the rails l9 lengthwise of the tube from the end of the tube adjacent the bearing ll to the end thereof adjacent the chuck l8. During this movement of the carriage 2|, the electrode 24 is guided to its proper welding position adjacent but slightly spaced from the line of juncture between the fin and the tube. The electrode is disposed within one or two fin turns of the roller 33 so that irregularities in the pitch of the fin along the length of the tube do not materially alter the position of the elecone manufacturer, and the flux employed in this process is conventionally termed the melt,

In order to supply the melt for the weld, a trough 25 is suspended from the under side of the floor 2!, the fioor 26 of the trough underlying the tube and its attached fin. The trough is partially filled with the melt in powdered form so that as the tube rotates, the end of the electrode properly guided to its correct position closely adjacent the line of juncture between the fin and the tube is surrounded by the melt. Additional melt is supplied to the trough 25 from time to time as required. A welded seam is thus formed in the triangular space between the edge of the fin and the adjacent tube wall as illustrated at l l in Fig. 3.

To maintain the electrode 24 accurately aligned with the axis of the tube during the movement of the carriage, the trough 2-5 is provided adjacent the forward end with guide jaws 21 which are shaped to fit the wall of the tube between two adjacent turns of the fin. The laws 21 are mounted for movement toward and away from the tube in any suitable manner, for example, as shown in Fig. 5, the bars carrying the jaws 21 may be mounted in guides 28 and held in adjusted position against the tube by set screws 29.

While the operation of welding the fins to the tube may be accomplished accurately and expeditiously with the apparatus disclosed, it will of course be understood that the welding may be accomplished by hand or with other types of welding apparatus.

It will be noted that the edge surface of the coiled fin is substantially at right angles to the 'face of the fin and consequently when the face of the fin is inclined tothe normal in the manner shown, the edge of the fin will also be inclined, thus forming a substantially triangular shaped groove between theedge of the fin and the adjacent wall of the tube which receives the molten welding metal and forms a strong welded joint, affording a. perfect heat-conducting connection between the metal of the tube and the metal of the fin.

The finned tube of the present invention forms an excellent heat radiating element with a greater heat-radiating surface for the same overall diameter of tube than obtainable with the conventional spiral fin tubing wherein the fin is perpendicular to the axis of the tubing.

The tubing is also particularly useful in heat exchangers for extracting heat from granular or pulverulent materialsv such, for example, as the solid catalyst materials employed in certai oil cracking operations. The inclined fin facilitates change surface of the fins and if the tubes are mounted with the edges of the fins extending downwardly the pulverulent material will fiow through the shell around the tubes in substantially uniform manner without clogging or formin Dockets. When the fin is normal to the axis of the tube the pitch of the fin must be very steep in order to prevent the pulverulent material accumulating in the spaces between the fins and checking the fiow of the material. With the inclined fin of the new type of tubing the pitch of the spiral is not relied upon to effect the downward fiow of the material but merely the inclination of the fin with respect to the axis of the tubing, and consequently a closely wound fin of comparatively fiat pitch may be employed, thus greatly increasing the available heat-conducting surface.

While I have shown the fin as joined to the tubing by a continuous welded seam, it is obvious that the steps of coiling the fin and spacing the fin on the tube with its axis inclined to the horizontal may be employed with other types of heatconducting bonds between the fin and the tubing. For example, the surface of the tube may be knurled or serrated as shown in U. S, Patent No. 1,992,297 and the fin wound against the tube under sufficient pressure to form between the fin and the tubing a type of joint such as disclosed in said patent with reference to the conventional radial fin. Also the tube may be grooved for the reception of the inner edge of the fin and the metal of the tube along the edge of the groove pressed against the fin to form a heat-conducting joint.

It will also be understood that the method and apparatus disclosed for welding the edge of the fin to the tubin may be employed in making conventional tubing with the plane of the fin normal to the axis of the tubing. For such purpose no modification of the apparatus disclosed will be required except the proper shaping of the electrode holder and the spacer guide roller to conform with the conventional radial fin.

Other changes in the procedure and apparatus may obviously be made within the scope of the appended claims.

I claim:

1. The method of applying a heat radiating fin to a tube which comprises coiling a strip of metal into a flat closely coiled helix having an internal diameter greater than the outside diameter of the tube, extending the tube into the coil, attaching one turn of the coil adjacent one end thereof to the wall of the tube, inserting between two adjacent turns of said coil a spacing roller having a straight element disposed at an acute angle to the axis of the tube and a perpiheral part disposed at an angle to said straight element, contacting said roller element and part respectively with the face and the outer edge of the coiled strip and effecting relative rotation and longitudinal movement of the tube and the spacing roller to extend the coiled strip along the tube and simultaneously contract the internal diameter of the coiled strip sufficiently to contact its inner edge with the wall of the tube and turn the plane of the strip to an acute angle to the axis of the tube.

2. Apparatus for spacing at pre-coiled, fiat,

radially-extending fin on a tube comprising means for rotating the tube, a support movable longitudinally of the tube and in parallelism therewith, means for shifting said support longitudinally of the tube in timed relation with the rotation of the tube, and a spacer member carried by said traveling support having only two fin-engaging and confining surfaces, one including a straight fin-face-engaging element extending radially of the tube at an acute angle to the tube axis, and the other including a part disposed at such an angle to said fin-face-engaging element as to adapt it to engage and confine a substantial portion of the outer edge surface of a fin when a fin face is engaged by said other surface, said spacer member serving to space the successive turns of a fin longitudinally of the tube and to bend the plane of a fin toward the tube at an acute angle to the axis of the tube.

3. Apparatus for spacing a, pre-coiled, fiat, radially-extending fin on a tube comprising means for rotating the tube, a support movable longitudinally of the tube and in parallelism therewith, means for shifting said support longitudinaily of the tube in timed relation with the rotation of the tube and a spacing roller carried by said traveling support and having only two tin-engaging and confining surfaces, one including a straight fin-face-engaging element disposed at an acute angle to the tube axis and the other being a peripheral shoulder disposed at such an angle to said fin-face-engaging element as to adapt it to engage and confine a substantial portion of the outer edge surface of a fin when a fin face is engaged by said other surface,said "fin-engaging and confining surfaces acting to space the successiveturns of a fin longitudinally of the tube and to bend the plane of a fin toward the tube at an acute angle to the axis of the tube.

ROBERT M. WALLACE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,151,721 Sahlin Aug. 31, 1915 1,217,537 Turney Feb. 27, 1917 1,738,994 Gredell Dec. 10, 1929 1,837,294 Scheid Dec. 22, 1931 1,909,704 Morseth May 16, 1933 1,950,623 Owston Mar. 13, 1934 1,981,566 Nigro Nov. 20, 1934 1,992,296 DeWald Feb. 26, 1935 2,039,690 Trainer May 5, 1936 2,155,394 Berg Apr, 25, 1939 2,179,881 Du Boscq De Beaumont Nov. 14, 1939 2,226,535 Payne Dec. 31, 1940 FOREIGN PATENTS Number Country Date 618,099 Germany Aug. 31, 1935 

